Since you have an exemption (you are married to a Vietnamese citizen?) If you are able to demonstrate your ability to speak & read English fluently and follow instructions, it's conceivable that someone would hire you legally as a teacher assistant, to lead classes with the assistance of a Vietnamese teacher assistant.
-@OceanBeach92107
I am sorry OB but isn't this just conjecture on your part? The brutal fact is that all WP's are subject to the determinations of the bureaucrats who grant them. I might add that properly credentialed ESL teachers make wages that are orders of magnitude greater than their Vietnamese counterparts. We should be grateful for the graciousness with which almost all public school Viet English teachers treat us. Not all, but most of those that I have encountered were sincere and conscientious teachers.
-@THIGV
Certainly my feedback is conjecture based on incomplete information, but that's because the OP is providing vague background information, leading me to say it's "conceivable" but not likely or probable.
It's easy to forget that you've been away from Vietnam for so long that you likely are not up to date on some current laws, such as those regarding work permit "excemptions" (quoting our budding undergraduate who perhaps has yet to successfully pass English 101 "online"):
Current Regulations Re: Work Permit EXEMPTIONS For Foreigners (link)
My reply to the OP is actually based on a real situation which happened in the fall of 2018.
The foreigner was in Vietnam during the first 90 days of a business visa and so didn't require an initial work permit to be employed at a language center in Quảng Nam province.
However, the native English-speaking foreigner was not qualified to be considered for a position as an ESL teacher.
So the school hired the foreigner as a "teacher assistant" for 30 days, while still paying them the same hourly rate offered to qualified native English-speaking ESL teachers.
The language center told the foreigner that there would be a "teacher assistant" in the classroom to help them.
It wasn't until later that the foreigner learned that their "assistant" was in fact a fully qualified and credentialed Vietnamese ESL teacher.
I've always been pretty consistent when expressing my view that many (if not most) foreigners hired as ESL teachers are simply giving schools/language centers an excuse to charge Vietnamese parents exorbitant tuition rates in return for receiving pronunciation & diction coaching.
As I've also previously mentioned, IMO, the current shortage of foreign ESL teachers is proof that far too many people who were previously filling those positions prior to COVID were not in fact fully qualified to do that work, otherwise there shouldn't be any hindrance in rehiring them and they never should have been denied permission to remain in the country.
I share your high regard for Vietnamese teachers who are fully qualified except for their lack of outstanding pronunciation/enunciation skills, and so receive significantly less than foreign "experts" whose technical qualifications are often inferior.